Single-piece fan wheel

ABSTRACT

The invention relates to a blower wheel (1) in a one-piece design having a bottom disk (12) and a cover disk (11) between which a blade ring is formed having multiple blower wheel blades (13) disposed in the circumferential direction at a spacing from one another, wherein the bottom disk (12) defines a maximum radial diameter da and the cover disk (11) forms an axial intake opening (25) having a diameter di, wherein the cover disk (11) extends radially outwards from the circumferential edge (14) which forms the intake opening (25) and has a maximum outer diameter dt, and wherein an outer diameter ratio dt/da is defined in a range from 0.6 to 0.8.

The invention relates to a one-piece blower wheel for use in a blower,particularly in a gas-air premix blower.

Blower wheels for use in a gas-air premix blower are known from priorart and comprise a bottom disk, a hub for connecting to a rotor of anelectric motor, and optionally a cover disk. Where a cover disk isprovided, a blade ring of blower wheel blades disposed at a spacing fromone another in the circumferential direction extends in the axialdirection up to the cover disk, forming a radial blowout section.

When in operation, oscillatory interaction occurs between the rotorwhich drives the blower wheel and the blower wheel itself, which couldhave an adverse influence on noise characteristics and air output of theblower wheel. It was found in practice that a pumping movement which hasan adverse effect on air output and noise characteristics is initiatedat a specific order, particularly the 8th order, of the naturaltorsional frequency of the rotor. Measurements have confirmed that thesound power increases significantly at a speed of the blower wheel thatis at the natural torsional frequency of the rotor.

It is therefore the object of the invention to provide a blower wheelthat is less susceptible to the pumping movement, particularly to axialvibration in the area of the outer diameter due to influences from thedriving rotor. Its fluidic properties (air output, speed, efficiency)and simple and economical manufacturing are to be maintained.

This object is achieved by the combination of features according toclaim 1.

According to the invention, a one-piece design of a blower wheel isproposed having a bottom disk and a cover disk between which a bladering is formed having multiple blower wheel blades disposed at a spacingfrom one another in the circumferential direction. The bottom diskdefines a maximum radial diameter da. The cover disk forms an axialintake opening having a diameter di and has a maximum outer diameter dt.The cover disk extends radially outwards from the circumferential edgethat forms the intake opening. An outer diameter ratio dt/da is definedin a range from 0.6 to 0.8, more preferably in a range from 0.66 to0.77.

Regardless of the blower wheel diameter, the advantageous effects ofreduced axial vibration during the natural torsional frequency and thusreduced acoustic emissions are always achieved in a blower wheel that ischaracterized in that the separation of bottom and cover disks at aratio of the outer diameters is set to a value of 0.69 or 0.74 with arespective maximum variation of ±0.03. The respective value cantherefore generally be applied.

Small changes of the ratio of the outer diameters dt/da have asubstantial influence on the interaction between the rotor and theblower wheel and particularly with respect to exciting axial vibrations.The range according to the invention of the ratio of outer diametersdt/da is small and even characterized by a specific selection of values.

The one-piece or single-part design of the blower wheel allows easydemoldability during manufacturing by injection molding and goodinjection molding properties. The blower wheel can also be producedcost-effectively using a 3D printing process.

In an advantageous embodiment of the blower wheel, the blower wheelblades start from the circumferential edge of the cover disk and extendradially outwards, and the axial front sides of the blower wheel bladesare uncovered and extend radially outwards on a side opposite the bottomdisk and comprise a free end each.

Furthermore, a design is advantageous in which the cover disk, viewed ina radial section, is curved in a funnel-shaped manner and forms an inletnozzle.

To achieve positive injection molding properties and a reduced tendencyto vibration excitation, a design of the blower wheel is favorable inwhich the cover disk has a thickness t at the circumferential edge whichcorresponds to a thickness t of the blower wheel blades. The same wallthicknesses generally are a preferred solution, such that it is furtherfavorable that the bottom disk, at least at its radially outer edge, hasa thickness t that corresponds to the thickness t of the blower wheelblades.

In a further improvement, a radial outer edge of the cover disk finallyalso has the thickness t of the blower wheel blades. Both the cover diskand the bottom disk can have a constant material thickness t over theiroverall radial extension.

Another positive aspect for reducing excitation and acoustic emission ofthe blower wheel is found in an embodiment in which a ratio of thediameter of the axial intake opening di and the maximum outer diameterdt of the cover disk di/dt is in a range from 0.5 to 0.7. The intakeopening therefore makes up a large portion of the entire diameter of theblower wheel, such that the radial extension of the cover disk is small.

A significant area for axial vibration excitation is the radially outersection of the blower wheel. In an advantageous embodiment for reducingvibration of the blower wheel, the radially outer edges of the blowerwheel blades extend in a plane parallel to the axis of rotation and thebottom disk is flush in a plane with the radially outer edges of theblower wheel blades.

Radially on the inside, a design of the blower wheel is advantageous inwhich the blower wheel blades transition into the hub of the blowerwheel on their radially inner sides. The radially inner edges of theblower wheel blades can extend in an arc-shaped cross section, such thatthey are rounded towards the intake opening.

It is furthermore favorable that the outermost radial sections of thecover disk and the bottom disk extend parallel to an axial plane, thatis, extend radially outwards in a straight line.

For manufacturing without a slider, a blower wheel design is favorablein which the bottom disk and the cover disk extend without overlappingrelative to one another in an axial top view, as viewed in a projection.

The invention further includes a blower designed as a gas-air premixblower for delivering a gas-air mixture, having a multi-part blowerhousing and a motor unit with motor electronics disposed on its outerside, wherein a blower wheel having the features described above isdisposed inside said blower housing which, when in operation, draws inair via an intake opening of the blower housing and blows out air via ablowout opening of the blower housing, wherein the motor unit includes arotor which is in operative connection with the blower wheel.

Other advantageous further developments of the invention are explainedin more detail below with reference to the figures as part of thedescription of a preferred embodiment of the invention. Wherein:

FIG. 1 shows a perspective view of an exemplary embodiment of a blowerwheel according to the invention;

FIG. 2 shows the blower wheel from FIG. 1.

FIGS. 1 and 2 show a one-piece blower wheel 10 having a bottom disk 12and a cover disk 11 between which a blade ring is formed having multipleblower wheel blades 13 disposed in the circumferential direction at aspacing from one another. The cover disk 11 comprises an axial intakeopening 25 having a diameter di, which extends in a funnel-shaped curvewhen viewed in a radial section and forms an inlet nozzle at the intakeopening 25. The outermost radial section of the cover disk 11 and theentire bottom disk 12 each extend parallel to an axial plane, that is,perpendicular to the axis of rotation of the blower wheel 1.

At its circumferential edge 14, which defines the intake opening 25, thecover disk 11 has a thickness t which corresponds to the thickness t ofthe blower wheel blades 13. The bottom disk 12 also has the thickness ton its radially outer edge 15 and is flush in a plane with an radiallyouter edge 18 of the blower wheel blades 13, which edge extends in aplane parallel to the axis of rotation of the blower wheel 1. Thematerial thickness t of the bottom and cover disks 12, 11 is constantfrom radially inside to radially outside over their overall extension.

The bottom disk 12 extends radially inwards from the radially outeredges 18 of the blower wheel blades 13 and directly covers sections ofthe axial front sides of the blower wheel blades 13, wherein the bottomand cover disks, 12, 11 do not overlap in an axial top view, as viewedin a projection.

The size ratios of the blower wheel 1 are essential in fluidic respectand for solving the technological problem. The bottom disk 12 defines amaximum radial diameter da. The cover disk 11 extends radially outwardsfrom the circumferential edge 14 which forms the intake opening 25 andhas a maximum outer diameter dt. The ratio of the outer diameters dt/dais a preferred 0.74 in the exemplary embodiment shown. Furthermore, thedi/dt ratio is at a value of 0.6. The maximum variation is ±0.3.

The cover disk 11 forms the part of the blower wheel 1 located radiallyinside on the intake side and covers sections of the blower wheel blades13 in the area of the intake opening 25. The bottom disk 12 covers theblower wheel blades 13 in the area located radially outside. The blowerwheel blades 13 extend in a straight line from the radially outer edge19 of the cover disk 11, but inclined radially outwards in thecircumferential direction. The axial front sides 17 of the blower wheelblades 13 have free ends and are uncovered on a side opposite the bottomdisk 12.

The blower wheel 10 further comprises a hub 16 into which the blowerwheel blades 13 transition on their radially inner sides, wherein theradially inner edges 20 of the blower wheel blades 13 are arc-shaped.

1. A blower wheel in a one-piece design having a bottom disk and a coverdisk between which a blade ring is formed having multiple blower wheelblades disposed in the circumferential direction at a spacing from oneanother, wherein the bottom disk defines a maximum radial diameter daand the cover disk forms an axial intake opening having a diameter di,wherein the cover disk extends radially outwards from thecircumferential edge which forms the intake opening and has a maximumouter diameter dt, and wherein an outer diameter ratio dt/da is definedin a range from 0.6 to 0.8.
 2. The blower wheel according to claim 1,wherein the outer diameter ratio dt/da is set in a range from 0.66 to0.77.
 3. The blower wheel according to claim 1, wherein the outerdiameter ratio dt/da is set to a value of 0.69 or 0.74 with a respectivemaximum variation of ±0.03.
 4. The blower wheel according to claim 1,wherein the blower wheel blades start from the circumferential edge ofthe cover disk and extend radially outwards, and the axial front sidesof the blower wheel blades are uncovered and extend radially outwards ona side opposite the bottom disk and comprise a free end each.
 5. Theblower wheel according to claim 1, wherein the cover disk, viewed in aradial section, is curved in a funnel-shaped manner and forms an inletnozzle.
 6. The blower wheel according to claim 1, wherein the cover diskhas at its circumferential edge, which defines the intake opening, athickness t which corresponds to the thickness t of the blower wheelblades.
 7. The blower wheel according to claim 1, wherein the bottomdisk, at least at its radially outer edge, has a thickness t thatcorresponds to the thickness t of the blower wheel blades.
 8. The blowerwheel according to claim 1, wherein a radial outer edge of the coverdisk has the thickness t of the blower wheel blades.
 9. The blower wheelaccording to claim 12, wherein the bottom and/or cover disk(s) have aconstant material thickness t.
 10. The blower wheel according to claim1, wherein a ratio of the diameter of the axial intake opening di andthe maximum outer diameter dt of the cover disk di/dt is in a range from0.5 to 0.7.
 11. The blower wheel according to claim 1, wherein radialinner edges of the blower wheel blades are arc-shaped.
 12. The blowerwheel according to claim 1, wherein it comprises a hub into which theblower wheel blades transition on their radially inner sides.
 13. Theblower wheel according to claim 1, wherein the outermost radial sectionsof the cover disk and the bottom disk extend parallel to an axial plane.14. The blower wheel according to claim 1, wherein the bottom disk andthe cover disk extend without overlapping relative to one another in anaxial top view, as viewed in a projection.
 15. A blower designed as agas-air premix blower for delivering a gas-air mixture, including amulti-part blower housing and a motor unit with motor electronicsdisposed on its outer side, wherein a blower wheel according to claim 1is disposed inside said blower housing which, when in operation, drawsin air via an intake opening of the blower housing and blows out air viaa blowout opening of the blower housing, wherein the motor unit includesa rotor which is in operative connection with the blower wheel.